B0158 code meaning
Ambient Air Temperature Sensor Circuit
What B0158 means
Although B0158 is absent from the publicly available J2012 lists, General Motors and Saab use it with exactly this meaning. In the 2011 Saab 9-4X the instrument cluster reads the outside air sensor and stores B0158 02 when the signal implies more than 88 °C, B0158 05 below −40 °C; the display then shows dashes. Saab 9-3 manuals place it in the body module: under 0.25 V means short to ground, above 5 V means open or short to supply, and the last known value is kept. GM bulletin PIC5656F (LaCrosse 2010–13, Verano 2012–16, Malibu 2013–16, Cascada 2017) links B0158 to a missing outside temperature and an HVAC display stuck in Celsius, and starts with the sensor plug and circuits 61 and 636.
B0158 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 1 hours
- Clears after repairWhen cleared with a scanner
Symptoms of B0158
- Outside temperature display missing or showing dashes
- Automatic climate control works with a stored or default temperature
- On some GM models the HVAC display switches to Celsius
Common causes of B0158
- Most likelySensor at the front bumper unplugged or connector damaged after front-end work
- PossibleThermistor in the outside air sensor open or shorted, often after stone impact
- PossibleSignal or low reference wire to the cluster damaged
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Ambient air temperature sensorInstrument clusterHvac control module
What each part of B0158 means
| B | Body system: airbags, seat belts, power seats, lights and climate control. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 58 | The exact fault in that area. |
What to do next
- Note B0158 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about B0158
What does B0158 mean?
B0158 means "Ambient Air Temperature Sensor Circuit". Although B0158 is absent from the publicly available J2012 lists, General Motors and Saab use it with exactly this meaning. It is a generic code, so it means the same on every make.
Is it safe to drive with B0158?
B0158 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will B0158 fail an emissions test?
B0158 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is B0158 to fix?
Difficulty: medium. A typical repair takes 0.3 to 1 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will B0158 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.